Transient loss minimization in induction machine drives using optimal control theory

Abstract

Loss minimization during transient operation is an often neglected in most induction machine applications. However, loss minimization can greatly improve efficiency in case of fast changing load torques or reference speed profiles. Optimal control theory has been successfully applied previously to develop control laws that minimize losses during transients. All previous works were based on the field oriented induction machine model. In this paper, however, an optimal control problem based on the non-field oriented induction machine model is developed and simulated. Additionally, a more comprehensive cost functional is developed and utilized that would guarantee a stable steady state operation of the machine. Offline optimal control histories are generated using the conjugate gradient method. The performance of the proposed control law is verified through simulation and the results are compared with those from an indirect field oriented controller.